The invention relates to a grease gun of the type having a tubular casing on one end of which fits a pump attachment and on the other end of which a cover is provided in which a draw rod extending into the casing is axially movable and fixable, a pressure collar in the casing on the draw rod and a compression spring between the pressure collar and the cover, the draw rod having a handle external to the casing.
In a known grease gun of this type, the handle whose width is greater than the diameter of the casing can be unscrewed from the draw rod and the casing can be unscrewed from the pump attachment so that the cover, the draw rod, the pressure collar and the compression spring can be extracted from and inserted into the casing through the pump attachment end. The cover has a relatively wide (about 10 millimeters) guide ring bearing on the rim of the casing from within so that it is relatively difficult to move the cover within the casing especially if the draw rod is not exactly coaxially loaded. As a draw rod fixing arrangement there is provided a keyhole-type guide hole in the cover and an annular tee-slot on the draw rod near the pressure collar.
Thus, only in its fully extended state, with the compression spring highly compressed, can the draw rod be fixed in a slanting position deviating from the center axis. When a cartridge, which contains grease and whose open end is to be guided into the pressure collar, is inserted into the casing, the insertion may present difficulties if the end of the cartridge is pinched, torn or bent. In particular, air from the sucked-in grease in the casing cannot be sufficiently removed from the grease because of the pressure of the compression spring so that, during greasing, air may be expelled instead of pure grease and this is frequently not noticed.
It is an object of the present invention to provide a grease gun where air, which may be present in the grease can be intentionally expelled from out of the casing without unduly complicating the construction of the grease gun.